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The nearest sunlike star with an Earth-size planet in its habitable zone may be only 12 light-years away.

David A. Aguilar / CFA

November 8, 2013

40 Billion Earths?

Astronomers find there could be tens of billions of nearby planets that support life

By Jennifer Marino Walters | for

Could there be life on other planets? A new report by astronomers says that as many as 40 billion habitable (able to support life) Earth-size planets could exist in our galaxy, the Milky Way.

The new information is based on data from NASA’s Kepler space telescope, which was launched into space in 2009 to search for potentially life-supporting planets orbiting other stars. Now, data collected using Kepler suggests that one out of every five sunlike stars in the galaxy has an Earth-size planet circling it in the “Goldilocks zone,” the distance from the star that produces the right temperature that would make liquid water possible.

“The nearest sunlike star with an Earth-size planet in its habitable zone is probably only 12 light-years away and can be seen with the naked eye,” says Erik Petigura, a University of California, Berkeley, graduate student and the leader of the team that studied the Kepler data. “That is amazing.”

HUNTING PLANETS

Kepler photographed the same 150,000 stars in the Milky Way about every 30 minutes for four years. The telescope scanned the skies for dips in the brightness of the stars that might occur when planets pass in front of them. The team estimated that 22 percent of all sunlike stars in the galaxy have Earth-size planets in their habitable zones. Since the Milky Way has about 200 billion stars, that adds up to about 40 billion planets.

But the researchers say that even though these planets are Earth-size and lie in habitable zones, they may not be able to support life.

“Some may have thick atmospheres, making it so hot at the surface that [life] would not survive. Others may have rocky surfaces that could harbor liquid water suitable for [life],” says Geoffrey Marcy, an astronomy professor at UC Berkeley. “We don’t know what range of planet types and environments are suitable for life.”

MORE TO LEARN

Kepler collected data for four years before it stopped working properly this past May. Scientists have gone through three years of that data so far. In that time, they have identified a total of 3,538 potentially habitable planets. Scientists will likely continue to study the data for decades.

According to Marcy, one thing is certain. The findings, he says, “represent one great leap toward the possibility of life, including intelligent life, in the universe.”